Decatur, Ill. (WAND) - Warm weather means more time for activities outside, like parties.

Ameren Illinois is asks people to be aware of a popular party accessory that could cause problems, if they aren't disposed properly.

"Something that seems so innocent can cause a huge issue," said Ron Pate, Senior Vice President of Operations and Technical Services for Ameren Illinois.

Mylar balloons are metallic and conduct electricity. When one of these balloons is released into the air and comes in contact with a power line it could cause surges and shorts. Ameren Illinois says, Mylar balloons have the ability to knock out power, start fires and cause significant damage.

"When people lose control of those balloons and they come in contact with our power lines they can cause significant outages to our customers," explained Kevin Young, Ameren Illinois.

Last May, more than 3,000 customers in southern Illinois lost power for a few hours because untethered Mylar balloons were tangled in overhead lines.

"We realize this is the time of year when everyone is outside celebrating new graduates, newlyweds, birthdays and spring holidays," said Pate. "Keeping the balloons tethered and weighted while in use and then properly puncturing and disposing after the fact can help to ensure they do not get loose and end up in our power lines and substations."

The popular party accessory can also pose a safety hazard for linemen who have to safely untangle and remove what's left of the balloons from energized high voltage lines.

"Keep them tethered. Don't let them go up and certainly don't release them," explained Pate. "You know even if they go up above the lines, what goes up must come down."

If you notice a balloon entangled in a power line, Ameren Illinois says to always assume the line is live and do not attempt to remove it. Instead, call Ameren Illinois at 1-800-755-5000 and a crew will be dipatched.