A freighter and a tanker loaded with 400,000 barrels of crude oil collided in clear weather and erupted into flames here early today, leaving at least four dead, 27 missing and feared dead and several others injured.

Throughout the day and into the night, the tanker spilled its cargo into a fiery slick that sent skyward a bank of smoke visible 40 miles away. Under it, Coast Guard vessels pressed their search until dark for any of the 30 or so missing crewmen of the 750-foot Liberian tanker, Burmah Agate.

Three of its crew of approximately 35 to 38 were found dead in the water, and one victim's body was on the deck as the ship burned. Four were treated at local hospitals. Two are listed in serious condition.

It was not known how many of the missing crewmen may still be inside the hulk.

But as the day wore on, officials acknowledged the growing likelihood that few of the missing had survived.

Nearby, the 480-foot Liberian freighter Mimosa, which was filled with ballast water after unloading a cargo of steel Wednesday night, circled for seven hours under unmanned power, forcing the temporary evacuation of several nearby oil drilling rigs. The Mimosa's crew of 26 abandoned ship, and an unknown number of them suffered burns, smoke inhalation and shock.

The ships collided at 5:08 a.m. about four miles offshore of this port city and near the entrance to the Houston ship channel. Traffic on the channel was interrupted, but later resumed normal operations.

Port of Houston officials said they did not know whether the advancing oil slick from the Burmah Agate would force a closing of the channel.

For hours, the oil spilled from a 7-by-15-foot gash in the starboard aft tanks of the Burmah Agate. So dense was the smoke that it hid much of the infero created by the burning oil. Several fires burned on deck, apparently fed from below.

The derelict Mimosa circled close by, still smoldering from a fire in an aft compartment, until the ship played out its fuel, or engines, about 1:30 p.m., and stopped dead in the water. A gash across the bow just above the water line gave it a grisly, shark-like grin.

Oil spill cleanup crews and equipment where standing by to confine and remove the slick, if necessary, from the waters of the Gulf of Mexico, which had six foot seas. But it appeared tonight that the slick was headed away from Galveston's popular recreational beaches.

Coast Guard crews were allowing the oil to burn to minimize the extent of the slick.

The active search for the missing crewmen was suspended at dark and was set to resume at daybreak. However an alert was broadcast for all ships in the area to be alert for any survivors.

There was confusion throughout the day as to how many men were aboard the Burmah Agate, and thus how many were missing. The size of the crew was variously put at 35 to 38, and Coast Guard spokesmen said all they knew was that there were four known dead and four known survivors. Thus the toll of missing ranged anywhere from 27 to 30, but was still subject to change.

Officials said visibility at the time of the collision was 15 miles, and the cause of the accident was not known. The investigation was being complicated by problems in communicating with the crews.

Chang Ying-Chuang, a 53-year-old crewman on the tanker, said through an interpreter that the loud explosion awakened him.

"There was fire and smoke everywhere," the Associated Press quoted him as saying. "We could not fight the fire. It was no use. Everybody else jumped overboard. We did not jump, so we were saved."

The tanker apparently was en route from New Orleans to Houston, and the freighter and unloaded steel in Houston Wednesday night. According to preliminary reports, both were under power at the time of the accident.

At the 5:08 a.m. distress call, a Coast Guard helicopter was dispatched from Houston. It hoisted the Mimosa's crew of 26 to safety when the flames spread out of control.

The ship's master told Coast Guard officials that the evacuation was conducted safely and that there were no injuries among the crew.

Two of the tanker's crew were reportedly treated and released.