MELVILLE, N.Y. (AP) _ Regional air controllers knew a Colombian jetliner was low on fuel and needed priority landing clearance 50 minutes before it crashed, but local controllers never got the information, investigators said.

The investigation into Avianca Flight 52's crash, which killed 73 people and injured 85, is focusing on the communication gap between the high-altitude air traffic controllers and those handling landings at three local airports, said Lee Dickinson, of the National Transportation Safety Board.

Dickinson said investigators planned to interview the regional controllers today. Investigators also returned this morning to the crash site in Cove Neck on Long Island. They were expected to end the on-site investigation later today or Tuesday.

Records indicated the Boeing 707 had more than enough fuel for the flight from Bogota and Medellin, Colombia, to New York, but the jet flew in three holding patterns totaling nearly 90 minutes along the East Coast because of weather-related congestion before it crashed Thursday night, investigators said.

As the plane neared the end of its final, 46-minute holding pattern south of Kennedy International Airport, the crew told controllers in the regional New York Center about the fuel shortage and requested priority clearance to land, Dickinson said.

At that point, controllers asked pilot Laureano Caviedes what his alternate landing site was, and, according to Federal Aviation Administration tapes, he replied, "Boston. I can't make it."

Shortly afterward, the regional controllers turned the aircraft over to the local controllers. But, after interviewing six local controllers who either handled or tracked the flight, investigators determined they were unaware of the shortage.

"For whatever reasons, we don't know, the controllers (handling landings at Kennedy) did not know that," Dickinson told reporters late Sunday.

"I don't know why it wasn't passed on. It may have been passed on in a different style, if you will," he said without elaborating.

He said the regional and local controllers had spoken to each other by telephone when transferring control of the plane.

At 9:24 p.m. the plane aborted an attempted landing at Kennedy, apparently because of bad weather, and the pilot immediately said he wanted to try again, saying twice to one of the controllers that he was low on fuel, Dickinson said.

That was the first time the local controller knew anything about a fuel problem, Dickinson said.

Less than 10 minutes later the plane crashed. The pilot and the other two members of the cockpit crew were among those killed.

A federal official close to the investigation who spoke on condition of anonymity said information obtained by investigators indicates the error appeared to lie with the regional controllers.

Dickinson emphasized that when the pilot told the regional controllers he needed a priority landing, the word "emergency" was never used and for that reason the severity of the situation may not have been relayed.

Asked what procedures would have mandated an emergency, he replied without elaboration: "There are certain phrases that the cockpit should tell the controller. The word 'emergency' was never used. The word 'priority' was."

Dickinson noted that an American Airlines flight that landed right before Avianca's aborted attempt had 14 minutes of fuel when it landed. The American pilot had told controllers he would declare a fuel emergency if he was not immediately cleared for landing.

Many pilots are reluctant to declare a fuel emergency because the FAA strictly monitors those cases, according to aviation officials. Should the agency determine a pilot was not justified in declaring an emergency, the pilot's license can be suspended.

"Pilots are not anxious to declare an emergency," he said, "because they then have to explain it to the FAA. The FAA comes in and says, 'OK, what's the emergency here?'"

"It's embarrassing," The New York Times quoted an unidentified pilot as saying. "Plus you have to write a lot of reports."

Investigators determined during the weekend that none of the Avianca's four engines was running when it slammed into a wooded hillside.

Investigators earlier said the plane may have had up to 10,000 pounds, or nearly 1,500 gallons, of fuel upon impact. But NTSB spokesman Mike Benson said Sunday that figure could be wrong because the fuel gauges may have given inaccurate readings.

Boeing spokesman Jack Gamble in Seattle has said that 1,500 gallons of fuel could have been enough to get the plane from the crash site to the airport 15 miles away, "but not much more."

Benson said the NTSB planned to calibrate and test the gauges.

The Boeing 707 fuel gauges cannot be trusted when the level goes below 10,000 pounds, said John Nance, a former Braniff pilot who is an airline safety analyst.

Officials changed survivor totals twice during the weekend. After officials compared Avianca's passenger list and hospital records, they revised the tally of people on board from 161 to 159; officials could not immediately explain the second change, to 158.

More than 20 survivors remained in critical condition, hospitals reported.