HONOLULU -- Four people died and three others were critically injured Thursday in a helicopter crash at Princeville Airport on Kauai, according to county officials.

It happened at about 3 p.m.

The helicopter apparently took off and was just two miles away before reporting the problems and turning around.

State transportation officials said the pilot knew there was trouble.

"Initial reports show the pilot made an emergency call to the airport and he was complaining about a hydraulics problem aboard the aircraft," Department of Transportation spokesman Scott Ishikawa said.

Shortly afterward, the helicopter crashed on the northwest end of the Princeville Airport, officials said.

Three people were declared dead at the scene. Paramedics treated the four survivors and took them to Wilcox Hospital. One of the victims died on the way to the hospital.

Heli USA said in a statement it is notifying the families of the victims. The company said it is not releasing the names of the passengers at this time because of privacy reasons.

The company said its condolences goes out to all who are involved.

Heli USA also said it is working with investigative authorities to determine exactly what happened.

The fatal crash comes just weeks after the National Transportation Safety Board said it wanted new tougher regulations on Hawaii tour helicopters. That call was prompted by investigations in two fatal chopper crashes on Kauai in recent years.

One of those crashes, the most recent, was on Sept. 23, 2005. Three people died and three others, including the pilot, survived the crash into waters off Kauai.

Last month, the federal government announced new safety standards for air tour companies that operate at many scenic vacation spots and for pilots who offer rides at air shows. The Federal Aviation Administration also promised to keep closer track of deaths and other accidents involving air tours.

The federal changes were sparked by crashes off Hawaii and Alaska.