Security investigators at a nuclear power plant in Ohio say that they have not made much progress in determining who left radioactive goldfish in an underground steam tunnel.

The Nuclear Regulatory Commission (NRC) announced earlier this month that it had launched an investigation after workers found two goldfish swimming in a lemonade pitcher filled with reactor water at the Perry nuclear power plant operated by FirstEnergy Corp.

The steam tunnel was monitored by video cameras, but investigators this week admitted that yellow protective radiological suits and including hoods made identifying suspects difficult.

"While we continue to look at the video for evidence, identifying folks in the video has been challenging," Perry spokesperson Jennifer Young explained on Tuesday.

The NRC has been monitoring the plant closely since 2011 when four workers were exposed to radiation.

"Last year, Perry got into trouble with the NRC about weaknesses preventing unauthorized access to the plant," David Lochbaum of the watchdog group Union of Concerned Scientists told The Plain Dealer. "Goldfish are not authorized to be inside the tunnel, yet they were there. And Perry cannot determine how they got there or who put them there. What if it hadn't have been goldfish but a bomb?"

"What might be an amusing account of misplaced goldfish today could become tomorrow's nightmare story if someone with an axe to grind, another Timothy McVeigh type, places a bomb instead of two goldfish in Perry."

Watch this video from WEWS, broadcast May 2, 2013.