San Diego

Two separate predawn bombings destroyed mailboxes and wakened residents Monday in Scripps Ranch and northern La Jolla, police said.

No one was injured in the blasts, which involved “quite powerful” devices, said Tom Taylor, an inspector with the U.S. Postal Service in San Diego.

The bombs, Taylor said, were “very sophisticated” and distinct from the standard homemade pipe-like devices that are frequently employed by amateur bombers. However, police said authorities had not immediately determined what type of explosives were used.

There was no known motive for the bombings, which occurred about an hour apart. Authorities would not say if the devices were intended to injure people or simply cause property damage. No suspects were in custody, police said.

Police would also not say whether the two incidents were definitively linked.

On Monday afternoon, Taylor said, postal inspectors received an anonymous telephone call claiming responsibility for the bombings. The caller made no threats, Taylor said.

The U.S. Postal Service is investigating the bombings, as is the Metro Arson Strike Team, which is composed of San Diego police and fire authorities.

The first bombing occurred shortly after 3 a.m. on the corner of Via Aprilia and Carmel Valley Road in northern La Jolla. Police responding to calls of an explosion in the area found a mailbox blown apart and pieces of mail scattered over the street, authorities said.

The second blast happened about an hour later at 9950 Avenida Magnifica near the Scripps Ranch area, police said. Officers found a similar scene of scattered correspondence and a destroyed mailbox.