(CNN) - The hunt for ISIS leader Abu Bakr al-Baghdadi is very much on.
CNN has learned that at one point over the summer the US believed they had their best shot at killing the terrorist leader in an airstrike, according to several US officials.
The strike, which has never been publicly disclosed, was based on intelligence that indicated a senior ISIS leader, quite possibly Baghdadi, was at the particular location. The officials familiar with the strike tell CNN it has never been definitively determined if Baghdadi was actually killed. But one official told CNN that over recent months "we tried to take several shots at him."
One reason the US remains uncertain if it killed Baghdadi is that in the days and weeks that followed the strike, US intelligence did not intercept any ISIS communications confirming his death and there was no discussion on ISIS social media accounts, US officials said. Given Baghdadi's stature, the US expects to see significant chatter discussing his death, if he is killed.
The strike occurred after a claim by Russia in June that the ISIS leader might have been killed in one of its airstrikes on the outskirts of Raqqa on May 28. The US has long believed that the Russian claim is not true.
In another instance CNN has learned that US military planners for a ground mission being conducted by US forces thought they were on Baghdadi's trail for a significant period of time. Intelligence indicated an individual with the name al-Baghdadi was at a target site, a US official confirmed to CNN.
Senior administration officials were briefed but a raid did not happen because of concern over the potential number of civilians at the site. The US official says they now believe Baghdadi was likely not at the location. It remains unclear if that individual was any relation to the ISIS leader.
A consistent problem the US has faced is that intelligence tips on Baghdadi's whereabouts are often not timely, meaning he is likely to have moved on before they are able to mount an operation to take him out. Baghdadi is believed to remain fairly mobile, often moving by vehicle with just a driver one official told CNN. Because he potentially remains on the move, the best chance of killing him might come with last minute intelligence that would require a strike by a drone already loitering nearby.
Over the last several months, the top US commander in Baghdad has given several tantalizing answers to reporters about Baghdadi's whereabouts. In a July 11 press briefing, Lt. Gen. Stephen Townsend told Pentagon reporters: "I'm unable to confirm or deny where he is or whether he is alive or dead."
Townsend recently departed Iraq after his tour of duty as commander was completed. In his final press conference on August 31, Townsend told reporters "I really don't know where he is." He then added "I believe he's alive? Yes. Why? Because I've seen no convincing evidence, intelligence or open source or other -- rumor or otherwise, that he's dead. So, therefore, I believe he's alive."
Without offering details Townsend also said "there are also some indicators in intelligence channels that he's still alive."
Officials say that now ISIS has largely been forced out of Raqqa as well as Mosul, they believe Baghdadi is somewhere in the middle Euphrates River Valley, which could put him in the crosshairs of the Syrian regime and Russian aircraft operating in the region.
Two administration officials also say that over the last several weeks the CIA assembled specific intelligence that prompted undisclosed drone strike missions carried out by the military mainly in Syria to go after ISIS targets. The CIA declined to comment on the matter.
Because of the lack of confirmation about Baghdadi's death, the working assumption by the US is that he still remains alive. Officials say they will continue to pursue him even though they believe that his relevance in the ISIS organization may be diminished as the coalition drives fighters out of its strongholds in Iraq and Syria.