SAN JUAN, Puerto Rico (AP) _ Small pipe bombs exploded simultaneously early Monday at a Citibank branch and a factory, causing minor damage but no injuries, police said.

A pro-independence group said it set the bomb at the Citibank to protest a planned 1991 plebiscite on Puerto Rico's relationship with the United States and the use of Puerto Rican soldiers in the Persian Gulf crisis. Police said the bomb destroyed the front door of the bank branch in Arecibo, 45 miles of San Juan.

No group claimed responsibility for a blast at an electrical switch factory in Vega Baja, about 20 miles west of the capital. The pipe bomb had been placed in an air-conditioning unit and caused minor damage.

Both explosions took place at 1:05 a.m. but it was not immediately known if they were related, said police spokesman Edwin Burgos.

The pro-independence group, the Revolutionary Armed Forces-Albizu Campos, claimed the Citibank bombing in a statement to a San Juan radio station. The group, which carried out two similar bombings last year, takes its name from independence leader Albizu Campos, who died in 1965.

Congress is considering legislation that would allow Puerto Ricans to vote in a plebiscite in June 1991 on whether to remain a U.S. commonwealth, become the 51st state, or form an independent nation. Polls indicate less than 10 percent of the population favors independence.

The Caribbean island of 3.6 million people has been a commonwealth since 1952. The status gives Puerto Ricans most rights of U.S. citizenship, but they cannot vote for president. They pay no federal taxes.