ST. LOUIS (AP) _ Four men, two of them brothers, have been arrested in the slayings of five people and the wounding of two others during a supermarket robbery, police announced Monday.

The arrests came after one of the men contacted authorities over the weekend and led officers to the others, said police Capt. Charles McCrary.

However, he said, ''We still have a lot to do to finalize our investigation.' ' Additional arrests were possible, he said.

The slayings were the worst multiple homicide in the St. Louis area since at least 1980, when four workers were shot to death during the robbery of a shopping center cafeteria.

Police said two men entered the northside National supermarket after it closed on Friday night, possibly while posing as a cleaning crew.

After money was removed from a cash register, seven store employees were herded into a corner and apparently ordered to lie on the floor. Most of them were shot in the head, police said.

Two of those who were shot survived and were reported in serious condition. Two other employees escaped injury by climbing onto the store's roof, police said.

McCrary said discrepancies in information given by the man who contacted police on Saturday led to the investigation's first arrest.

''During further questioning of the suspect on this subject, he admitted to being in the company of several other men who were responsible for the actual robbery and the homicides,'' McCrary said.

He declined to provide details of the questioning or say why the man contacted police.

McCrary said one of the three who were subsequently arrested Sunday eventually implicated all four of those who were charged.

Those charged in the killings were identified as Charles Wright, 36, Anthony Benn, 27, Reginald Williams, 23, and his brother Ricky Williams, 19.

Wright, Benn and Reginald Williams were charged with first-degree murder, armed criminal action, assault, robbery and burglary. Ricky Williams was charged with second-degree murder, McCrary said.

McCrary declined to specify which of the four men contacted police and which were believed to have carried out the killings.

A weapon was recovered Sunday but investigators were not certain it was the same one used in the killings, McCrary said.

Police have not ruled out the possibility that the robbery was an inside job. Mike Monica, 28, the store's frozen food manager, said janitorial employees arriving at the store shortly after 11 o'clock Friday night were not asked to show identification and apparently knew they would be able to slip into the store.