San Francisco police said they are recovering today from the largest gathering ever in the Castro District for Halloween night, during which there were four stabbings and about 30 arrests.

With a record crowd around 300,000 people - or double the typical number -- the celebrated costume party started out in the jovial vein for which it has been known over the years, according to Sgt. Nick Rubino. But by 11 p.m., the mood for some had shifted.

"All of a sudden, it went downhill,'' Rubino said. He said the number police incidents this year was the highest ever, and some people threw bottles at officers but there were no mass arrests.

Two stabbing incidents were reported shortly after 11 p.m. in the vicinity of the 18th and Market street event. A woman's face was slashed with a razor during an argument with someone she knew, and a group fight between possible gang members occurred in which one person was critically stabbed in the stomach.

Rubino said two other, less serious, stabbings took place not long after at nearby gas stations, one at a Chevron station at 17th and Castro and another at an ARCO station nearby. The sergeant said he had few details on those cases.

The swelling crowd caused police to close off the area between Market and Dolores streets, or two blocks more than usual, and hampered efforts to get ambulances in where needed. Rubino estimated as many as 60 percent were from out of town, even as far away as Oregon.

"People were spewing out of BART and (San Francisco) Muni,'' the sergeant said. They started to head home around 2 a.m. when bars close.