FRESNO, Calif. — A transient was booked on suspicion of murder Tuesday for allegedly slashing the throat of a Greyhound bus driver with a pair of scissors, causing a crash that killed two passengers.

The bus, heading from Los Angeles to San Francisco, flipped on its side Monday evening and slid into a field off Interstate 5 near Fresno. It was carrying 50 passengers.

The suspect, Arturo Martinez, 27, was held on two counts of murder and one count of attempted murder. Authorities said they did not know of any motive.

``He has told us several stories about why he did what he did,'' sheriff's Lieut. Margaret Mims said. She said authorities were checking to see whether drugs, alcohol or mental problems played a role.

According to witnesses, the man rose from his seat shortly before 9 p.m., walked briskly up to the driver and attacked him with the scissors. The driver survived.

``It happened very quickly. He immediately stabbed the driver, too quickly for the passengers to take action on their own,'' Mims said. She said the driver ``struggled, tried to defend himself and lost control of the bus.''

Authorities caught Martinez as he tried to run away.

Lynn Brown, a Greyhound Lines spokeswoman, said 26 passengers and the driver were taken to hospitals. Three people, including the driver, remained hospitalized Tuesday at a Fresno hospital, where they were listed in fair condition.

Alfredo Saravia, a passenger from suburban Los Angeles, said he was awoken by the attack.

``The people in the front, when they saw, they tried to stop the guy, but he already had the driver. Everything happened in seconds,'' he said. ``The bus started tumbling and went off the road and started flipping.''

Almost exactly a year ago, on Oct. 3, 2001, a passenger on a Greyhound bus in Tennessee cut the driver's throat, causing a crash that killed seven.

Two weeks later, passengers on a Greyhound bus in Utah helped thwart an alleged hijacker. And in November, a Greyhound passenger angry that he wasn't allowed to smoke scuffled with a driver in Arizona, causing a crash that injured 33.

Greyhound, the largest bus service in the United States with 20,000 daily departures, has hired a private company to screen some passengers with electric wands but has inspectors at only a portion of its terminals.

Congress has included $3.8 billion US in an anti-terrorism bill passed this year to augment aviation security. It has approved $15 million for security improvements on intercity buses.