SAN JOSE, Costa Rica (AP) - An earthquake with a preliminary magnitude of 6.7 shook Costa Rica early Friday, and was felt in neighboring Panama and Nicaragua. There were no immediate reports of casualties or damage. The earthquake occurred at 4:02 a.m. local time, said Don Blakeman, a geophysicist at the National Earthquake Information Center in Golden, Colo. The epicenter was 55 miles south of San Jose, the capital. Temblors of magnitude 6 can cause serious damage. Blakeman said he had no early reports of damage but "wouldn't be at all surprised considering the magnitude" if there was some damage.