LOS ANGELES (AP) — Firefighters called to a Los Angeles apartment building Thursday found one person dead, three others ill in what may be carbon monoxide poisoning, officials said.

A report that someone was ill sent a crew to the four-story building in Koreatown around 5:45 p.m., fire spokesman Brian Humphrey said.

One person was found dead, he said, and at least three other people came forward to say they were ill, Humphrey said.

They were being evaluated, he said.

Hazardous materials experts were sent into the building with sensors.

"We have discovered the presence of carbon monoxide at elevated levels" after firefighters forced their way into many apartments, Humphrey said.

Firefighters in breathing gear examined 48 apartments but no other patients were found, Humphrey said.

"Many of the units we discovered were empty, no one in there. Others were in the building (but) exhibited no signs of illness," he said.

The building, which was built in 1928, was evacuated, he said.

Humphrey said another person was found dead in the same building recently but it was unclear what was the cause of that death.