Guatemala's President Otto Perez has lowered to 42 the number of victims killed in a powerful earthquake that toppled homes and cut power this week in several towns in the country's southwest.

"The number that we have at the moment is 42 confirmed dead, and two people are still missing," said Perez late Friday of the quake that caused most of its destruction in the town of San Marcos.

The toll is ten fewer than the number officials had originally believed perished in the disaster, which struck on Wednesday.

Some 16,000 people were affected by the 7.4 magnitude quake off Guatemala's Pacific coast, which was this country's most violent seismic event since 1976 when almost 23,000 people perished.