HOUSTON -- Deer Park officials issued a level three shelter-in-place warning Monday morning after a gas leak was discovered at the Dow Chemical Plant, News2Houston reported.

Traces of the chemical napthalene, which is used to make mothballs, were discovered outside the plant's boundaries around 6:15 a.m.

The city of Deer Park was notified and officials issued the level three warning, alerting people to stay indoors, keeping doors and windows closed, until further notice.

Officials are not sure what caused the chemical leak.

Dow Chemical Plant officials are working to get the situation under control.

The shelter-in-place warning was removed around 8 a.m.

Shelter-In-Place Order

Emergency crews issued a shelter-in-place order for nearby residents.

When a shelter-in-place is issued, residents should:

Go inside
Shut all doors and windows
Turn off air conditioners and heaters to prevent outside air from getting inside
Stay off the phone
Do not use fireplaces. Put out fires and close all dampers.
Move to a room with the fewest windows and doors. Tape around doors, windows, exhaust fans and vents using plastic sheeting or garbage bags, if directed.
Turn on the radio or television to listen for further instructions

Families are advised to have the following items in a shelter-in-place kit.

Two rolls of duct tape
Cloth and paper towels
Plastic sheets or trash bags
Flashlight and extra batteries
Battery-powered radio
Two gallons of water
Nonperishable foods

If your eyes, nose or throat become irritated, protect your breathing by covering your mouth with a damp cloth, take frequent shallow breaths and stay calm.