By Homer Bigart
Special to The New York Times

SANTIAGO DE CUBA, April 8 - A loud explosion rocked Santiago de Cuba tonight causing a flurry of nervous firing by Government troops stationed on rooftops throughout the city.

The explosion, believed to be caused by the rebel underground, completely wrecked the warehouse of the Cuban Air Products Company, a subsidiary of the Air Reduction Corporation of New York. It went off at 8:30  P. M..

One hundred-pound canisters for compressed gas hurtles across the Avenida de Balgica, five blocks from the army’s Moncada Barracks. Three pedestrians were wounded. The night watchman of the warehouse was reported missing.

Meanwhile, residents of the city expressed fears that the Government’s apparent decision to bar newsmen from Orient Province might foreshadow brutal repressions.

They felt that as long as foreign correspondents were in Santiago the security forces of the Batista dictatorship would be inhibited from staging mass arrests and executions.

Three United states correspondents were released this morning from military detention. But the three, and four other United States newsmen were warned through the United States Consulate to leave the city immediately.

After conferring with Brig. Gen. Alberto del Rio Chaviano military commander for Oriente Province, Parks Fields Wollam, United States Consul, called the seven correspondents and pleaded with them to return to Havana.

He said the United States Government could not protect them from harassment by the security forces of the Batista regime. He added that General Chaviano had told him that he “wished” the newsmen would “depart.”

Asked for an interpretation of the, Mr. Wollam said: “It is not a command, but you might as well take it as a command.
 
“We can’t be responsible for your safety. You are liable to be picked up again” and the security forces “ won’t be so polite.”

Mr wollam said that Oriente Province was under martial law and that the security forces could do anything they pleased.

He had not protested the fact that Ben silver, a reporter for television station WCKT in Miami, had been held incommunicado by the army since Saturday night. Army authorities had not notifies the Consulate of Mr. Silver’s detention . Mr. Silver was still confined as Mr. Wollam spoke, but the consul said he had assurances of early release.

The three correspondents who were frees this morning were Ray Brennan of the Chicago Sun-Times, Ed Cannel of the Newspaper Enterprise Association and Alan Jarlson of radio station KRAM, in Las Vegas Nev. Army intelligence officers had seized the three men in the lobby of the Casa Grande Hotel last midnight.

Three other newsmen, Robert Taber of the Colombia Broadcasting System, Harold Lidin of The United Press and this correspondent also were taken to Moncada Barracks but e\were released thirty minutes later.

Mr. Brennan, Mr. Cannel and Mr. Jarlson were held a little more that nine hours before they were released about 9:30 A. M..