RIYADH, 21 January — Interior Minister Prince Naif denied reports yesterday that the Euromarche blast that occurred on Jan. 10 was caused by firecrackers and said explosives like TNT might have been used.

"After thorough examination at forensic labs, it was found that the blast was not from firecrackers. Explosives like TNT were used. We believe that it was caused by an irresponsible party," he said.

Prince Naif was talking to reporters before leaving for Sanaa to sign an agreement with his Yemeni counterpart for the appointment of an international company to mark border points between the two countries.

Prince Naif said that according to preliminary investigation, the Euromarche blast has no connection with the previous bombings in Riyadh and Dhahran that killed a Briton and injured five other Britons.

Prince Naif said efforts to implement the Saudi-Yemeni border treaty were going in the right direction. He hoped the offer of the German company selected for the work would be reasonable, adding that the project would be completed in four years.

Prince Naif, who later arrived in the Yemeni capital, said the Saudi-Yemeni Joint Committee had gone a long way in implementing the border treaty.

The Saudi minister said the committee would discuss entry points on the border. Prince Naif said a security agreement between the two countries would tackle individual cases, but refuted allegations that Saudis were involved in blasts in Yemen. "We reject such allegations," he added.