National Transportation Safety Board investigators were at the scene Sunday where six Pasadena police officers were injured in a collision of two helicopters at the department's heliport in Altadena, about the time the USC-UCLA game was ending in the Rose Bowl.
Both helicopters were severely damaged, but none of the six officers was seriously hurt, police said.
The crash happened about 4 p.m. at the heliport at 2175 Yucca Lane, apparently as one helicopter was taking off and the other was landing.
The main rotor of one chopper apparently hit the the other.
Members of the NTSB team were poring over the crash site for clues. Investigators were expected to interview the pilots in the next few days.
Each Bell OH-58 chopper contained a pilot and an observer, all of whom were taken to a hospital to be checked out, police said. Two officers on the ground also suffered minor injuries.
One helicopter had been monitoring the football game and the other had been on patrol over Pasadena, department spokeswoman Lt. Phlunte Riddle said.
"Until we have an opportunity to interview the pilots ... it's speculative to say who was coming and who was going," she said.
Pasadena police have four other helicopters in service.
The OH-58 design, widely used by the U.S. Army and available in several models, was introduced in 1969.