MEXICO CITY, JULY 31 -- Behind closed doors at a local hospital today, Mexican investigators began interrogating the American pilots of a U.S. cargo plane that slammed into a crowded highway here last night in a crash that claimed at least 40 lives.

Grieving relatives buried many of the victims today. {Ten badly burned bodies remained unidentified late this evening, an official told the Associated Press}. Sanitation workers interred the charred remains of championship show horses also killed in the crash.

Most of the dead were motorists whose cars were crushed and incinerated beneath the flaming fuselage of the Miami-bound Boeing charter plane, which crash-landed on a major highway less then 10 minutes after its 5:01 p.m. takeoff from Mexico City's international airport. One of the 12 people on the plane died, six are known to have survived and five are missing, according to Elsa Valencia, of the Attorney General's office.

Piloted by a three-man American crew, the approximately 40-year-old propeller-driven plane was carrying 18 prize jumping horses and nine passengers, most of them riders, grooms and trainers associated with a leading Mexican equestrian club. The plane was scheduled to deliver the horses to Miami, from where they were to travel to junior-level international jumping competitions in Virginia and Massachusetts.

Scores of drivers heading out of the city at dusk in a pounding rain maneuvered frantically as the plane approached the road, striking a high-tension electricity pylon in its descent, witnesses said. At least 26 cars and a 20-unit roadside apartment building were destroyed as the aircraft skidded 300 yards down the highway, police reported.

Witnesses from the ground watched as the craft flew over the city from the airport, steadily losing altitude and dangerously skirting two of the capital's tallest skyscrapers. Executives at Mexicana, a state-owned passenger airline, said they watched nervously out their windows as the crippled plane narrowly avoided the company's 32-story office tower.

"We were more than a little startled," said Jose Henonin, a Mexicana public relations officer, who said the plane passed within about 800 feet of the building at an altitude of barely 600 feet. "We don't often see planes at that height."

Henonin and others at the Mexicana office "were quite surprised that at no time did the plane seem to make any effort to reverse course" and head back to the airport on the city's less populated eastern side, he said.

Leased to a Belize-based company identified by Mexican officials as Belize Air International Ltd., the plane is owned by Agro-Air of Miami, Fla., according to U.S. Embassy officials. Inspectors from the U.S. National Transportation Safety Board are expected to arrive here soon for an on-site investigation.

One of the survivors of the crash, Guadalupe Pina Cardenas, a groom, told reporters that an apparent electrical failure had sent sparks showering from the plane's control panel minutes before the crash. Crew members abandoned the flight cabin shortly before the plane hit the ground, said Pina.

Some Mexican commentators, noting that the pilots flew their crippled plane across the densly populated city center while apparently failing to alert local traffic controllers about their difficulties, have suggested that there might be grounds for criminal prosecution.

"They have been advised to stay where they are and get a lawyer," a source familiar with the case said of the American pilots.

None of the four Americans aboard was seriously injured. The four were identified by U.S. officials here and Belize Air International in Miami as as Robert Banta, of North Bay Village, Fla.; Frederick Moore, of Hialeah, Fla.; Forrest Wooten, of Dade County, Fla.; and Brian Stewart, a horse trainer. All today were reported by examining doctors to be in "good to excellent condition," a U.S. Embassy spokesman said.