LONDON (AP) _ Police said Monday they are considering filing criminal charges over the late-night sinking of a pleasure boat by a dredger on the River Thames in which 25 people perished and 38 are still unaccounted for.

Divers, aided by more than two dozen police launches, continued to search the tidal river and salvaged hull of the Marchioness for more bodies from the accident early Sunday - the worst on the Thames this century.

Police reported 87 people survived.

Investigators said they have a list of 38 names ''who we have strong reason to believe were on board but are as yet unaccounted for.''

The 90-ton Marchioness had been chartered for a birthday party with guests from the modeling, photography and banking worlds. It collided with the Bowbelle, a 1,475-ton sand-and-gravel dredger, and sank in minutes.

Police said they have released the dredger's captain and second mate, who were detained after the accident, but expected to question them again. They said they also questioned the five other members of the dredger's crew.

A police spokeswoman said investigators were considering filing charges of ''unlawful killing,'' similar to manslaughter, but refused to say who might be charged.

Police, the Department of Transport's Marine Accident Investigation Branch and the Port of London Authority were investigating the accident.

The Independent and Evening Standard newspapers reported a disagreement had developed between the captains of the two vessels over which craft had the right of way under the central span of Southwark Bridge, where the collision occurred.

''It seems that both captains thought that they were in the right, but technically the actions of both could be held up to scrutiny,'' the Evening Standard quoted an unidentified river authority source as saying.

Jane Carmichael of Tidal Cruises, the firm that owns the Marchioness, said that although smaller craft usually stick to the side arches Marchioness Captain Stephen Faldo was correct to move through the center early Sunday because of tide conditions.

''We do not know what went wrong,'' she said. ''Our captain was acting totally correctly.'' Faldo is missing.

Scotland Yard declined to comment on the newspaper reports.

Police said they listened to tape-recorded radio traffic between the captains of both vessels and shore control for clues to the crash.

After visiting the accident scene, Transport Secretary Cecil Parkinson announced new safety rules including making charter vessels record the number of passengers and give them airline-style safety instructions.

The new requirements, effective Tuesday, came amid lawmakers' calls for increased safety on the Thames.

Parkinson also announced more Port of London Authority river patrols and random inspections of passenger vessels.

''We want to learn from this and make sure it doesn't happen again,'' said Parkinson, who cut short a vacation abroad after being informed of the accident.

Relatives of victims tossed flowers into the water near the site where the Marchioness sank. The stretch of river reopened for normal traffic but tour boats did not operate in honor of the dead.

As the tide dropped, the hull of the Marchioness became fully visible, resting on its side in a mudbank, the dance floor exposed to the bright sunshine. Seat covers, menus and bits of debris floated to the surface of the river.

The boat went down shortly after leaving for a 1 a.m.-to-dawn cruise celebrating the 26th birthday of London financier Antonio Vasconcellos. He is among the missing.

The double-deck Marchioness was struck from behind and run over by the dredger, according to investigators. The pleasure boat's top deck was sheared off.

Scores of people who had been drinking and dancing below deck were carried down with the hull as the boat sank quickly.

The last serious accident on the Thames occurred in 1878, when the Princess Alice paddle steamer was struck by a coal carrying ship. About 700 people perished.