A powerful bomb hidden inside a van has exploded in a parking garage at the Barajas International Airport in Madrid. All air traffic was immediately halted on one of the busiest travel days of the year. The blast occurred near terminal four; all flights to and from that terminal remain suspended. Twenty-six people are reported injured and one man is reported missing.

Reuters’ Jason Webb reports from Madrid:

One person was still missing after the explosion which brought down several concrete floors of the multi-storey car park at about 9 a.m. (0800 GMT), an hour after the first of three telephone warnings of an attack at Barajas Airport’s ultra-modern Terminal Four, officials said.

The BBC reports that two of those injured were police officers examining the vehicle and that there is “chaos at the other three terminals.” CNN reports that the Spanish government has blamed the blast on “Basque separatist group ETA.”

Spanish Interior Minister Alfredo Perez Rubalcaba said the government condemned the attack, “which breaks nine months without violence on the part of ETA, which breaks the permanent ceasefire.”

A Spanish interior ministry official earlier said two calls had been received by police, the first a warning, the second specifying the type of car and claiming it was the work of ETA.

More from Reuters:

Officials received three telephoned warnings about a bomb in a purple Renault Traffic van in the hour before the explosion, one of them claiming responsibility for ETA.

Police cordoned off the carpark area before the bomb blew up, sending a huge pall of smoke over the airport terminal.

In March of 2004, four separate explosions tore through the Madrid subway system killing 191 and wounded more than 1,700. Immediately after the blast, Spain’s former Interior minister assigned blame to Basque separatist group ETA.

Reported by the BBC several hours after those explosions:

No group has admitted responsibility but Spain’s government blames Basque separatist group Eta for the attacks which come ahead of Sunday’s election.

“There is no doubt Eta is responsible,” said Spain’s interior minister.

That attack was later proved to be the work of Islamic terrorists.

The ETA, listed as a terrorist organization by the United States, has targeted Span’s airports before including Zaragoza Airport, one of the country’s smallest airports and located in the north west. CNN reported on a possible mortar attack near that airport in June of 2005.

ETA often makes warning calls ahead of its attacks, to a Basque newspaper, Gara, which Friday reported on its Web site that it received “an anonymous call in the name of ETA” at 11:15 a.m. local time.

Gara reported that “two mortars” exploded near the Zaragoza airport.

However, a spokesman for the central government’s main office in Zaragoza said he could not confirm they were mortars, although he said police found “the impact of at least one projectile” and also found “three launchers” near the airport.

Unlike this morning’s attack at Barajas International Airport, or the 2005 alleged attack at Zaragoza Airport, the deadly Madrid train bombings did not come with a warning from anyone claiming to be with the ETA. More than 800 people are reported to have been killed by ETA violence since the 1960’s.

Earlier in the week, a car bomb exploded in a parking area outside the Peshawar Airport in Pakistan. The bomb was planted in a parked car. A airport worker writing a ticket was injured. No one has yet claimed responsibility for the blast.