Jerusalem (CNN) -- Dubai's police chief said Sunday the secretive Israeli foreign intelligence unit Mossad "needs to be ashamed" after the January killing of a Hamas leader in a Dubai hotel.

"I am now 100 percent sure that the Mossad is behind the assassination" of Mahmoud al-Mabhouh, said Lt. Gen. Dahi Khalfan Tamim. "I used to say 99 percent but now I can say 100 percent."

Al-Mabhouh, a founding member of Hamas' military wing, was found dead in his Dubai hotel room on January 20. Police believe he was killed the night before, and have identified some 26 suspects in his death.

Israel has a stated policy on security matters of neither confirming or denying involvement. Foreign Minister Avigdor Lieberman, however, told Israel Army Radio earlier this month, "There is certainly no reason to think that the Mossad and not some other intelligence agency of another country operated there."

Lieberman has also said only "media reports" link Israel to the slaying.

Asked about the case on Saturday, Israeli Defense Minister Ehud Barak repeatedly refused to make any comment.

"You know me long enough to assume that when I tell you I have nothing to say about this story, I have nothing to say, and I will not say," Barak told CNN's Christiane Amanpour.

"The Mossad needs to be ashamed of its actions," Tamim said Sunday. "They sent 26, 27 persons to assassinate one man who was involved in the capturing and killing of two Israeli solders." Hamas has said al-Mabhouh was behind the 1989 deaths of the two soldiers.

Earlier Sunday, police said toxicology results showed that al-Mabhouh was injected with succinylcholine, a drug used to relax muscles during surgery or as an anesthetic, before he was suffocated. Signs indicated that al-Mabhouh resisted as he was being suffocated, police said.

Family members were told earlier that police had found blood on a pillow. Authorities have also said the killers left some of al-Mabhouh's medication next to him in an apparent effort to make the death appear natural.

But "the medication left next to him in the room has nothing to do with the killing," Tamim said Sunday.

However, authorities have recovered evidence including DNA, he said. "The DNA evidence is quite important and will help us with the investigation."

The 26 suspects are believed to have acquired false passports to travel to Dubai for the killing, then scattered to several far-flung locations afterward.

But "not all the 26 people have forged passports," Tamim said Sunday. "We know some of the names are real."

The 26 do not include two Palestinians previously arrested in Jordan and returned to Dubai. Tamim said one is not believed to be directly involved in al-Mabhouh's death, but "he is wanted by one of the Palestinian factions in the Palestinian territories and he is sentenced to death and that's why we will extradite him." He refused to discuss anything about the other Palestinian.

Twelve of the suspects used British passports, police said. Six suspects used Irish passports, four used French passports, three used Australian passports and one used a German passport.

On Sunday, the British Embassy in Israel said it plans to talk to the British nationals whose identities were stolen and passports were used.

"We have made contact with six of the individuals and look to locate the remaining six for the fraudulent use of their identities," an embassy official said Sunday.

The meetings will take place at the embassy, the UK Serious Organised Crime Agency said.

"We are arranging to speak to them as potential witnesses to a crime," a spokesman for the agency said.

Tamim said Dubai does not plan to restrict travel in the wake of al-Mabhouh's death. He said al-Mabhouh entered the country under a false name and was not reported as being wanted by Israel. "If we knew that he was a wanted man and that he was coming to the UAE, we would not have allowed him in."

He said Dubai bears no ill will toward Israel or the Jewish people, "but we hate the hands, any hands that are covered with blood, whether they were Arab, Jewish or Muslim."

CNN's Caroline Faraj, Saad Abedine, Per Nyberg and Guy Azriel contributed to this report.