BATON ROUGE — Relatives of a 14-year-old girl who died when an oil storage tank exploded in February have sued the company that operated the tank.

The suit against Urban Oil & Gas Group and its insurer was filed Wednesday in federal court in Lake Charles by the mother, father, adult sister and twin brother of Zalee Day-Smith.

Day-Smith is believed to have been sitting on the tank near her mother’s house in Ragley when it exploded on Feb. 28. She was thrown into the air and her body was found hundreds of yards away from the tank site. The lawsuit says Day-Smith and family members thought the tanks weren’t being used.

“The absence of security measures or signage led decedent and plaintiffs to believe that the battery was inactive and abandoned, whereas it was actually active and dangerous,” the complaint states.

The company didn’t immediately respond to an email Monday. Urban Oil officials have previously told The Advocate of Baton Rouge that they have sympathy for Day-Smith’s family while broadly defending their safety record and declining further comment.

The 14-year-old girl’s death has already prompted Louisiana regulators to establish new rules to fence off oil field tanks and to try to identify all such storage tanks, called tank batteries, that aren’t connected to pipelines statewide.

The lawsuit blames Urban Oil & Gas for not monitoring conditions at the tank site, not properly maintaining the tank, not fencing off the tank site and not putting up warning signs.

The new state rules require operators to surround sites with fences at least 4 feet (1.2 meters) high, with a gate that’s locked when the sites are unattended. Tank hatches have to be securely sealed when unmanned, unless they’re part of a pressure relief system, and signs have to note the hazards of the tanks.

These regulations apply to sites within 500 feet (150 meters) of a highway or a home, 1,000 feet (300 meters) of a school or church, or anywhere within the limits of a city, town or village.

A 2011 report by the U.S. Chemical Safety and Hazard Investigation Board highlighted the dangers of not having warning signs and fences at storage facilities. It noted that 44 people were killed and 25 were injured in 26 explosions from 1983-2010.