Rescue workers picked through twisted wreckage and ruined homes today, looking for victims in Friday's crash of a Pan American World Airways 727 jetliner as federal safety investigators explored whether rain and severe winds played a role in the accident.

Theories that the plane was hit by a lightning bolt as it took off from Moisant Airport here lost ground as about 25 witnesses interviewed by the National Transportation Safety Board generally agreed that the three-engine jet was not struck.

The search teams, using a crane, turned the plane's blue-and-white tail section over and recovered two flight recorders that investigators hope will help pinpoint the cause of the crash, the second worst air disaster in U.S. history.

All 145 passengers and crew members aboard the jet died after it struck a residential neighborhood in the New Orleans suburb of Kenner. Impact occurred at 5:11 p.m. EDT, moments after the fully loaded plane lifted off during a heavy thunderstorm for a flight to Las Vegas.

Officials remained unable to give a firm count of the death toll, but Kenner Police Chief Sal Lentini said seven persons on the ground also were killed and that another person died later in a hospital.

The plane struck electrical wires as it went down, which may have created sparks that witnesses mistook for lightning, safety board vice chairman Patricia Goldman said.

At a news conference tonight, Goldman also said that a tape of radio conversations between the control tower and crew contained routine messages and no distress call.

In the hour before the crash, wind speeds varied from two to 25 knots, she said. The plane veered slightly to the left after lifting off, and about 2,250 feet beyond the runway it clipped a tree 53 feet above the ground. Witnesses gave no consistent account as to whether the jet hit the ground nose up or nose down, Goldman said.

A safety board laboratory in Washington is to begin analyzing the flight recorders Sunday morning.

One records the cockpit crew's words and sounds, such as engine whine and the clicks of controls being activated. The second, the flight data recorder, plots altitude, heading, speed and vertical forces.

The Kenner neighborhood resembled a war zone, with 13 homes damaged or destroyed and burned-out vehicles littering the streets. Shredded metal and landing gear were strewn on the lawn of one roofless home.

Louisiana Gov. Dave Treen toured the stricken neighborhood and said he planned to issue a disaster declaration to help speed restoration of services. "This is an awful tragedy, very, very grim and very depressing," Treen said.

The governor called in National Guardsmen to help residents whose homes were ravaged.

In Santa Barbara, Calif., vacationing President Reagan was "shocked by the loss of life" in the crash, deputy White House press secretary Larry Speakes said.

Bodies were being moved to a temporary morgue at the airport for identification. With many of them badly burned and dismembered, investigators were relying on fingerprints and other evidence. Tonight, only 19 of 112 bodies recovered from the wreckage had been identified, Goldman said.

National Transportation Safety Board investigators also began moving the wreckage to a hangar at Moisant Airport, where it is being cataloged. The plane, a Boeing 727, was delivered to National Airlines in 1968; National was taken over by Pan Am in 1980.

During the day, a safety board photographer took pictures of the crash site from a helicopter to assist in recreating the jet's angle of impact.

Witnesses have consistently reported that the plane crashed in an extremely heavy rainfall, though precise conditions of visibility and wind remain unclear.

Goldman stressed that it is too soon to draw any conclusions on the cause of the crash. But among aviation experts, initial speculation centers on weather as a contributing factor. The following points are being mentioned:

* "Wind shear." Pilots use this term for rapid changes in wind velocity and direction that can occur in thunderstorms and on the edge of moving fronts of air. If encountered at low altitude, wind shear can be extremely dangerous because the pilot does not have sufficient height to recover from any loss of control.

At times, wind shear creates a "down burst," in which energy is pent up in a storm, then suddenly expelled downward with force enough to drive any plane passing underneath toward the ground.

Such a down burst was blamed in the crash of an Eastern Airlines 727 on approach to Kennedy Airport in New York in 1975. One hundred and thirteen people died in the accident.

There is some debate in the industry over how to cope with wind shear. Instruments have been developed for use both in cockpit and on the ground to monitor it. The airport at New Orleans was using wind-shear monitoring devices at the time of the crash, Goldman said. She did not provide their readings, however.

* Water-logged engines. In 1977 a Southern Airways DC9 lost power in both its engines due to "ingestion of massive amounts of water and hail," the safety board concluded. Seventy people died as the plane attempted to land in New Hope, Ga.

Some witnesses have said the Pan Am jet's engine noise stopped before it hit. One aviation specialist pointed out that flames can shoot from a jet engine's exhaust when they go dead, possibly accounting for one witness' report of flames.

Analysis of the engine noise on the cockpit tapes could reveal whether the engines did, in fact, shut down.

Pilots had played down the lightning theory, since lightning in itself causes no significant damage to a plane. The danger occurs if it ignites stray fuel fumes and starts a fire or explosion, an extremely rare occurrence.

Whatever had disabled the plane, its ability to recover would have been impeded by the fact that it was carrying a full load of passengers and 44,000 pounds of fuel for its flight to Las Vegas. But there is no indication that the plane was overloaded or its cargo was improperly balanced.

Speculation also turned on whether the pilots had felt pressured to take off or had hesitated about going in such bad weather, but there were no answers today.

Friday's accident is the third major crash in the New Orleans area in recent years. In one of them, 19 people were killed when a Delta DC8 struck the Hilton hotel at the airport in 1967. Today, the hotel is the headquarters for the safety board's investigation of the Pan Am crash.