AFP - A van loaded with a bomb exploded Monday in the east of Madrid but no one was injured in the blast, a Spanish Red Cross official told AFP.
  
An anonymous caller warned the Red Cross at 7:30 am (0630 GMT) that there would be an explosion, giving the police time to clear the area before the blast.
  
According to Spanish national radio, the blast went off at around 9:00 am (0800 GMT). According to one local office worker it happened at about 9:05 am.
  
"When I arrived at the office at 8:25 am, the police were everywhere, there were helicopters overhead," said Simon, a 29-year-old French citizen working in the district.
  
"Police had set up a security cordon. We were told that there was a bomb alert, that we should stay away from the windows. And all of a sudden 'boom'."
  
The blast was strong enough to rattle the windows and shake the computers on their work stations, he added.
  
The explosion was in the Campo de las Naciones district of the city, on Ribera del Loira street.
  
Although the Red Cross official said there had been no casualties from the blast, a police spokesman was not able to confirm this.
  
He did say that the blast happened an hour and a half after the warning and that officers had managed to locate the vehicle it exploded.
  
No one has yet claimed responsibilty for the explosion, but the radio speculated that it could be the work of the armed Basque separatist group ETA three weeks ahead of regional elections in Spain's Basque region.
  
ETA carried out a car bomb attack in the same district a few weeks before the February 2005 regional elections, loading a car with 30 kilos of explosives. That blast injured about 40 people.