Another attempt last night to bomb the Spanish National Tourist Office, 338 Biscayne Blvd., fizzled as did the first try on March 19.

The detonator, however, fired this time. In the first attempt, nothing exploded and an employee reporting for work at 9 a.m. found the bomb.

He thought it was trash and threw it out on the sidewalk where it was later recognized for what it was. The bomb squad hauled it away.

In both tries, the bomb was shoved through the mail slot in the front door. After the first try, employees of the tourist office nailed a piece of plywood over the slot inside the door.

The would-be bombers knocked the plywood off and shoved the bomb through the slot anyway.

When the detonator blew last night it merely scattered the C4 plastic explosive around the office, police said.

After the first try, Joaquin Pujol, manager of the tourist office, said the bomb probably was planted by Cuban exiles who oppose Spain's trade with Castro's Cuba.

This time no one at the office would comment.

The try last night was the ninth bombing or bombing attempt in Miami since January 1. All but one target had a Latin flavor.