Strong Mexico Aftershock Rattles a Nervous Nation : Latin America: Terror hits again with 5.5 tremor. Thousands flee swaying buildings in Mexico City.

A strong aftershock hit the shattered Mexican state of Colima on Thursday, sending tremors through the nation’s capital and terrifying thousands of people left homeless by a deadly 7.6 earthquake three days before.

Red Cross and disaster relief officials reported isolated injuries Thursday after debris fell from homes and buildings badly damaged in Monday’s quake. That temblor, centered near the resort town of Manzanillo, killed more than 50 people.

U.S. scientists in Golden, Colo., said the aftershock measured 5.5 and was centered in the ocean, about 25 miles west of Manzanillo.

In Mexico City, tens of thousands of frightened office workers abandoned swaying high-rises during the 10:55 a.m. tremor.

Police said a 35-year-old maintenance worker was recovering after he was electrocuted during the aftershock. He was painting an electrical pole when the quake hit, and he grabbed a high-tension wire to steady himself.

There was no major damage reported in the capital or in Colima from the 29th--and most powerful--aftershock officially recorded since Monday’s quake, but it compounded Mexico’s struggle to recover from two natural disasters that have left tens of thousands of people homeless this week.

“The people are nervous. They’re desperate, and they still don’t want to go back inside their houses,” said Ernesto Flores, a Red Cross official in Colima’s village of Cihuatlan, where eight people died Monday and 12,000 are still sleeping in emergency shelters or in the street.

State officials in Campeche on the opposite coast reported that at least 42,000 people were homeless Thursday after Tropical Storm Roxanne flooded vast areas of the Yucatan Peninsula.

The storm, downgraded from a hurricane, also left several thousand people stranded on the resort island of Cozumel, which remains without power, water and telephone service, although there were no reports of serious injuries or major damage there.

U.S. and Mexican meteorologists reported that Roxanne had moved into the Gulf of Mexico but that it still threatened Mexico’s northern coastal states. The National Hurricane Center in Miami indicated that it could reach land as early as tonight.

Mexico’s national oil company said it had begun to normalize operations in the oil-rich gulf region after cutting back 70% on production of gas and oil in advance of the storm. But major seaports in the region remained closed for a third day, and exports were not likely to restart until today.

Against the backdrop of the twin disasters, the Mexican Red Cross appealed for a wide array of international assistance, including canned food, milk, medicine, clothing, soap and other necessities.

The post-quake relief efforts, Red Cross officials said, were especially strained in Colima and coastal regions of Jalisco.

In Cihuatlan, relief coordinator Mario Alonso Marques reported that a nearby hospital was badly damaged and that 12 people were injured in Thursday’s aftershock. Most, he said, were hurt by falling walls in structures that were damaged Monday.

Estela Aguilar, an office worker in nearby Coahuayana in the neighboring state of Michoacan, agreed that the aftershock’s impact on an already traumatized people was devastating.

“We still haven’t gotten over what happened on Monday, and now this comes,” she said. “Yes, we’re scared.”