NEW ORLEANS (AP) - A chartered bus carrying members of a seniors casino club on a Mother's Day gambling excursion swerved off a highway, careened down an embankment, then crashed up a grassy slope yesterday morning, killing 23 people, authorities said.

Eighteen more were hospitalized, nine in critical or guarded condition. Three people were released after emergency room treatment.

Mayor Marc Morial said it was the worst traffic accident in city history.

All bodies were not removed until four hours after the crash. ''We have people on top of each other, crushed between twisted metal,'' police Officer Joe Narcisse said.

The bus, traveling eastbound on Interstate 610, swerved from the left lane off of the highway, then across a narrow paved narrow path for golf carts that emerges from a tunnel next to the highway, crashing down one embankment and up the other.

It came to rest on a flat grassy area, where it passes through one of the city's biggest parks.

Terrell Walker, safety director for Custom Bus Charters, which chartered the bus for the trip to Casino Magic in Bay St. Louis, Miss., said the driver told him the bus swerved when it was cut off by another car. The bus originated in La Place, La., 26 miles west of New Orleans.

A witness told the same story. Linda Watkins said she was driving behind the bus when a white car swerved in front and the bus changed lanes. Then the white car swerved back in front of the bus, which ran off the road and crashed.

''People started flying out of the bus, flying out the windows,'' she said.

Authorities said the accident happened shortly before 9 a.m. as the bus was headed for a casino on Mississippi's Gulf Coast.

Walker said 46 people were on the bus, but the list of passengers was lost in the wreckage. Those aboard included members of an informal gambling club, many of them elderly, some in their 80s.