WASHINGTON (AP) _ The head of the Immigration and Naturalization Service vigorously defended his agency Thursday against claims that improper pursuit policies led to the deaths of six bystanders during a high-speed auto chase in California.

The pursuit policies of the U.S. Border Patrol, which is part of the INS, have been under scrutiny since last month when six people died in Temecula, Calif., after being struck by a vehicle carrying a dozen illegal immigrants. The vehicle had been pursued by Border Patrol agents.

''Despite some reports to the contrary, the Border Patrol acted responsibly,'' INS Commissioner Gene McNary told a House Government Operations subcommittee. ''Those who argue that these agents are wild and reckless are badly mistaken.''

McNary defended the need for high-speed chases but denied that Border Patrol agents were in pursuit at the time of the crash in front of a high school. He said the chase was ended after the Border Patrol vehicle's sirens and flashing lights malfunctioned a few minutes before the crash.

But Temecula Mayor Kay Birdsall disagreed.

''There's an obvious question of whether or not there was a pursuit. Our law enforcement says there was,'' she testified.

INS data shows that the Border Patrol was involved in 3,664 high-speed chases in southern California in the past 18 months. Those chases resulted in 121 accidents in which 12 people died and 44 were injured.

The Border Patrol is writing new guidelines that would place tighter restrictions on high-speed chases. Under the plan, agents would have to obtain go-ahead from a supervisor to engage in a chase as well as notify state and local law enforcement agencies.

The National Border Patrol Council, the agents' union, opposes those changes on grounds they are too restrictive, the union's president testified.

McNary and several House members used Thursday's hearing as a platform to stress that the nation's immigration policies - not high-speed chases - are hurting people.

''Washington's ongoing indifference to the problem of illegal immigration is the real villain in the Temecula incident,'' said Rep. Ron Packard, R- Calif. ''The tragedy is that illegal immigration is costing innocent people their lives.''

''The Temecula tragedy is one sad result of an ill that will continue to plague the nation as long as uncontrolled masses of people enter along the southern California border,'' McNary said. ''The real solution is control of illegal immigration.''

McNary noted that both House and Senate committees in recent weeks have rejected a request for 200 additional Border Patrol agents.

Rep. Byron Dorgan, D-N.D., has introduced a bill that would stiffen penalties for those who flee from law enforcement officials and ensure national uniformity in some pursuit guidelines.

Dorgan, whose mother was killed when her automobile was struck by a driver being pursued by authorities, said high-speed chases are a necessity.

''I have come to understand the law enforcement officers are not the villains,'' he said.