TOKYO (AP) _ A small, Japanese squid-fishing boat collided with a 4,531-ton Soviet cargo ship today in the Sea of Japan, and four crewmen from the squid boat were missing, the coast guard said.

Katsuhiro Muto of the Maritime Safety Agency's office in Niigata, northwestern Japan, said the four missing included the skipper of the No. 23 Horyo-maru. The boat capsized shortly after the collision.

There were no reports of injuries among 28 crewmembers aboard the Soviet Raychikhinsk, he said. The Soviet vessel was heading for Hiroshima from Vanino, a Soviet port, carrying 5,300 tons of coal, Muto said.

The collision occurred about 30 miles west of Sado Island, about 160 miles northwest of Tokyo, Muto said.

Three coast guard patrol boats and two aircraft were searching for the missing Japanese, the official said.

The cause of the collision was under investigation. The sea was reported calm at the time of the accident.