RAMALLAH, West Bank - Palestinians launched an investigation Monday after seven people were hospitalized when one of them opened a suspicious envelope addressed to Prime Minister Ismail Haniyeh, officials said.

The Cabinet building in the West Bank city of Ramallah, where the envelope was delivered, was evacuated, said Deputy Prime Minister Nasser Shaer.

The envelope contained an orange tissue that emitted a strong smell, said Shaer's office manager Abdel Basit Moatian, who opened the mail. Moatian said it had a Tel Aviv, Israel, postmark.

Haniyeh, a leader of the militant Hamas group who heads the Palestinian government, said he believed this may have been an Israeli attempt to kill him with "poison gas." He provided no evidence for the allegation.

Israeli officials declined to comment on the report.

A security guard who handled the envelope and another woman in the room were hospitalized and given oxygen, local hospital director Hosni Atari said. Atari said they were complaining of strong headaches and had fainted, but were now conscious.

Five other people who came in contact with the envelope, including Moatian, were briefly admitted for checks, he said.