An investigation by a House committee into the deadly attacks in Benghazi, Libya, on Sept. 11 found 13 instances of alarming events in the months before the attack that killed four Americans, prompting diplomats to make repeated requests for heightened security.

Those incidents were outlined in a letter to Secretary of State Hillary Clinton on Tuesday, with a request that the State Dept. reveal whether or not it was aware of these attacks and explain what steps were taken to beef up security.

The committee wants a response from Clinton by Oct. 8 and a hearing on the issue two days later.

The letter, written by Republican Reps. Darrell Issa of California, chairman of the House Oversight and Government Reform Committee, and Jason Chaffetz of Utah, stated that the earliest attack happened as early as April.

Many of the incidents explained in the letter are not directly related to the U.S. diplomatic presence in the eastern Libyan city, but one that was especially cause for concern took place in June, when Ambassador Chris Stevens -- who later died in the Sept. 11 attack -- was forced to stop his morning run for about a week after a post on a pro-Moammar Gadhafi Facebook page broadcast the location of the run and made a threat against him, according to the letter.

“Put together, these events indicate a clear pattern of security threats that could only be reasonably interpreted to justify increased security for U.S. personnel and facilities in Benghazi,” the letter read.

The lawmakers didn’t reveal who their sources for the investigation were, but they said they are people who have direct knowledge of the events.

“Based on information provided to the committee by individuals with direct knowledge of events in Libya, the attack that claimed the Ambassador’s life was the latest in a long line of attacks on Western diplomats and officials in Libya in the months leading up to September 11, 2012,” the letter read, adding that repeated requests were made for more security but were denied. The attack “was clearly never, as administration officials once insisted, the result of a popular protest.”

However, Clinton has said on multiple occasions that the Libya attack was an act of terrorism. She also said that al Qaeda affiliates may have been involved. An investigation into the attacks, by the Obama administration, is still under way.

Meanwhile, Libya and the United States have yet to agree how to cooperate in a probe of the Benghazi attack, a senior Libyan official told Reuters Tuesday.

So far, FBI agents have conducted interviews in Tripoli but have yet to go to Benghazi.

Deputy Foreign Minister Mohammed Abdel Aziz said the prosecutor general had given only verbal approval for a joint investigation.

"We are getting ready for the FBI team to go to Benghazi and meet with our team and start joint investigations together and also visit the site," he said.

"The FBI team is now in Tripoli. There are others who will come maybe soon to join the team ... Hopefully in the coming days we will reach an agreement as to how the (U.S.) team will work with the Libyan team ... We are now in the context of (awaiting) written permission."

Abdel Aziz spoke after meeting U.S. Assistant Secretary of State for Near Eastern Affairs Elizabeth Jones in Tripoli. "It is the right of the United States to be involved, exchange information and investigate what happened in Benghazi," he said.

State Dept. spokeswoman Victoria Nuland sidestepped the question of whether an agreement had been reached with Libya, but said: "We have a commitment from the Libyan government to work together. There has been cooperation at the political level. There has to now be cooperation at the investigative level."

While on his diplomatic mission, Stevens -- an Arabic speaker with long experience in the Muslim world -- was reportedly worried about the security threats in Benghazi, the rising Islamic extremism in the region and being on al Qaeda’s hit list, according to CNN.