About 50 African migrants are missing off the Canary Islands after their boat sank, survivors say.
Spain's Canary Islands are struggling with a migrant influx
Spanish coastguards picked up 48 of the Africans after their boat capsized about 145km (89 miles) southwest of the island of Tenerife.
Some of those rescued said about 100 people had been on board the open fishing boat. A search is under way.
On Wednesday at least four people died when two fishing boats carrying migrants sank between Italy and Libya.
Italian coastguards said 36 people were rescued in the incident, some 64km (40 miles) from the tiny island of Lampedusa.
Italian media report that another boatload of 259 migrants arrived at Lampedusa on Thursday.
The holding centre at Lampedusa is now packed with about 900 migrants, yet its capacity is 190, Italy's Il Messaggero website reports. Italy is starting an airlift to move migrants to other holding centres.
Spanish officials have said that in the incident off the Canaries rescuers tried to stabilise the vessel packed with migrants. They began ushering those on board to safety, but during the operation the fishing boat capsized, plunging dozens of migrants into the sea.
In 2006 an estimated 30,000 immigrants were caught trying to reach the Canary Islands.
The vast majority sailed from west Africa in crowded open boats, many dying en route.
An EU agency, Frontex, has begun operations to help Spain, Italy and Malta intercept migrant boats, but EU officials say it needs more resources.