Officials in Madrid said Friday they have not heard from anyone aboard a Spanish-owned oil tanker hijacked this week off the coast of West Africa, despite a statement from the Philippine government that the 23 crewmen were released safe and sound.

Neither the Spanish Foreign Ministry nor the ship's owner, Consultores de Navegacion, have been able to establish contact with the Mattheos I or its crew since the announcement from Manila early Friday.

Armed pirates seized the ship on Wednesday in the Gulf of Guinea.

Five members of the crew are Spanish citizens.

A spokesperson for Consultores de Navegacion, Sheena Campbell, expressed surprise over the statement from the Philippine government.

"The situation remains the same," she told Efe, adding that the company is doing "all it can" to secure the safe return of the crew.

Speaking for the Spanish government, Public Works Minister Jose Blanco said authorities had received no new information and stressed that they were handling the matter with "intelligence, prudence and discretion."

Miriam Losada, mother of Spanish crewman Damian Aguin, said she and her family were worried and that the press has been their only source of information on the hijacking.

The staffing firm that hired the crew, Ibernor, based in the northern Spanish city of Bilbao, said that besides five Spaniards and 14 Filipinos, the Mattheos I was carrying two Ukrainians and two Peruvians.

One of the Peruvians is the ship's skipper, Capt. Luis Alberto Chamochumbi.

The 48-year-old Chamochumbi did not encounter any pirates on previous voyages in the Gulf of Guinea, his sister Carmen told Efe.