UPDATE: The Hinds County Sheriff’s Office has closed its investigation into the lock-in and McDaniel’s supporters will not face any charges.

Barring some disaster, Chris McDaniel’s tea party-backed primary challenge to Mississippi Republican Sen. Thad Cochran looked likely to succeed on Wednesday morning. After all, McDaniel already weathered one lurid scandal in which four supporters were arrested for allegedly plotting a nursing home break-in. Surely his campaign could make it to the June 24 runoff without another bizarre police investigation, right?

Well, maybe not. The Hinds County Sheriff’s Office announced Wednesday that it was investigating three McDaniel supporters who were locked inside the local courthouse, where primary ballots were held, on election night.

Unlike the nursing home arrests, which involved prominent backers of McDaniel but no one directly tied to the campaign, the courthouse lock-in included a top McDaniel staffer, campaign coalition director Scott Brewster.

According to the McDaniel campaign it was an innocent misunderstanding. The campaign said it had dispatched three people to the courthouse to monitor the outstanding election night count, and they were accidentally stuck. They then called the local county executive, Pete Perry, a Cochran supporter, for help.

The sheriff’s office, however, isn’t convinced. The investigation is driven by the McDaniel supporters’ inability to get their story straight, a spokesman for the sheriff’s office said.

“There are conflicting stories from the three of them, which began to raise the red flag, and we’re trying to get to the bottom of it,” Othor Cain, a spokesman for the Hinds County Sheriff’s Department, told The Clarion-Ledger on Wednesday. “No official charges have been filed at this point, but we don’t know where the investigation will lead us.”

As spokesman for McDaniel did not immediately respond to a request for comment on Cain’s claim their supporters provided inconsistent explanations. But in a statement, the campaign said the three people were let in by security at the courthouse before discovering they had been left behind:

“Last night with an extremely close election and Hinds being one of the last counties to report, our campaign sent people to the Hinds courthouse to obtain the outstanding numbers and observe the count. “In doing so, they entered the courthouse through an open door after being directed by uniformed personnel. They were then locked inside the building. At this point they sat down and called the county Republican chairman, a close Cochran ally, to help them get out. Eventually a Sheriff’s officer showed up and opened the door to let them out.”

The sheriff’s office, however, cast doubt on the campaign’s version of events.

In an interview with msnbc Thursday, Cain said his office only provided security during normal business hours while off-duty officers worked late on election nights. But those off-duty officers should have been gone by the time the McDaniel supporters arrived.

“There are a lot of discrepancies in that story,” Cain said. “They closed the building down and locked it up at 11:30 p.m. that Tuesday night, which essentially means there were no off-duty officers on duty for them and none of my guys on duty for them. To say a uniformed officer let them into that building at that time of night is a total fabrication of the truth.”

Cain added that some non-uniformed courthouse employees, such as attorneys, have access inside and that the investigation was trying to determine whether anyone could have let the McDaniel supporters inside the building after hours. But the campaign’s initial claim of “uniformed personnel” was a red flag to his office.

“That’s one of the reasons we’re investigating. They say a uniformed person – they can’t identify what agency they’re with or what agency they represented,” Cain said.

Perry, the pro-Cochran Hinds County executive, told Talking Points Memo that trapped McDaniel supporter Janis Lane called him at 2 a.m. Wednesday morning asking for help, but that the version of events Lane gave him was different than the explanation later on Wednesday. For one thing, Lane had said she was trapped with a female friend rather than the two men who ended up being found in the courthouse, Brewster and conservative activist Rob Chambers.

Connie Cochran, the senator’s sister-in-law and an election commissioner, told TPM that no election materials were disturbed, to her knowledge, but that she was skeptical of the McDaniel campaign’s explanation given that she thought she was the last person to leave the building at 11:30 p.m.

MSNBC reached out to Lane for comment through the Central Mississippi Tea Party, where she is a board member. The group did not immediately respond to an e-mail request.

Cochran’s campaign, which had already run ads vaguely implying a connection between McDaniel and the nursing home arrests, jumped on the news to try and sow more doubts about their opponent’s.

“It is astonishing that the same people who are up to their eyeballs in four felons breaking into a nursing home are also up to their eyeballs in potentially breaking in somewhere else again,” Cochran campaign spokesman Jordan Russell told The Clarion Ledger.