Authorities on the Portuguese island of Madeira scrambled Monday to repair storm drains and clear debris from riverbeds, attempting to prevent a repeat of the landslides that killed 42 people over the weekend.

Rescue teams used sniffer dogs to search for at least four people still missing since flash floods and rock slides crashed through hillside villages and coastal towns.

The Portuguese government announced three days of mourning for the victims of Madeira's worst disaster in living memory.

SLIDESHOW: Portugal Swept Away in Mudslide

Crews in the capital, Funchal, pumped water out of a shopping mall's underground parking lot, where they feared they might find more bodies. The lot's two levels were submerged Saturday, when the rainfall of a normal month poured down in just eight hours.

A nearby street was littered with earth-filled cars and stacks of catalogues used as stepping stones through the mud.

Anais Fernandes, a store clerk, described seeing the water knock out a bridge.

"People were crossing, and you started to hear screams," she told Associated Press Television News. "Everyone was running together. It was horrible."

Rescue teams dug cars out of mounds of sludge to see if anyone was inside. Sniffer dogs scoured debris blocking the streets.

Emergency crews used bulldozers and front-loaders to remove tons of caked mud, boulders and snapped trees from drains and rivers, hoping to speed water runoff.

"We've been going flat-out for 48 hours and we'll keep going till the job's done," Funchal mayor Miguel Albuquerque said.

Locals were jittery as showers swept in, dumping more water on sodden hillsides.

Conceicao Estudante, the regional head of tourism and transport, told a news conference that 18 victims still had not been identified. She asked family members to go to a makeshift morgue at Funchal airport.

Seven members of an eight-member family died when their hillside home was swept away, public broadcaster Radiotelevisao Portuguesa reported.

Officials said 18 of 151 people admitted to Funchal's main hospital were still being treated. Some 150 people were homeless.

Rui Pereira, the Minister for Internal Administration, said in Lisbon the government was sending a second batch of aid to the island.

A military transport plane was heading to Madeira with more sniffer-dogs, high-powered pumping equipment and equipment for army sappers to replace collapsed roads and bridges, Pereira said. He said Madeira's financial needs were still being calculated.

Madeira, a popular tourist destination, is the main island of a Portuguese archipelago of the same name in the Atlantic Ocean just over 300 miles (480 kilometers) off the west coast of Africa.