The largest oil refining complex on the East Coast caught fire Friday morning after a butane tank caught fire at the Philadelphia Energy Solutions facility in South Philadelphia and set of a chain of explosions culminating in a massive boom.

This explosion is one of several major incidents to occur at facilities that operate on dirty fuel in major American cities in the past six months. An explosion at a Con Ed electrical facility turned the New York City sky aqua in December. In March, the Intercontinental Terminals Company petrochemical facility in Houston suburb La Porte, Texas experienced a massive fire and burned for four days. Residents were asked to shelter in place.

The City of Philadelphia asked residents to shelter-in-place just before 7 a.m., and the order was lifted shortly after 8 a.m. Philadelphia’s Public Health Department said in a tweet that the city's Air Management Services took samples at the refinery and in the immediate community “found no ambient carbon monoxide, hydrocarbons (combustibles), or hydrogen sulfides”—all toxic chemicals that are commonly found in oil refinery facilities. According to the AP, there were no reports of injuries, but one PES employee complained of chest pains and reportedly received treatment.

Craig Murphy, Philadelphia’s deputy fire commissioner, told the AP that the fire was “contained but not under control” at 7 a.m. PES did not return Motherboard’s requests for comment. When Motherboard contacted the Philadelphia Fire Department, Motherboard was told to contact PES.

According to NBC Philadelphia, warning sirens were issued at approximately 5:30 a.m., waking some residents. CBS News reported that the Philadelphia sky was lit up bright orange and yellow at the time of the explosion. Some New Jersey residents reported feeling the explosion from their homes.

PES is operated by oil and gas companies that have a history of major incidents related to their assets. PES is operated by Sunoco, according to the company website. Sunoco is a subsidiary of Energy Transfer Partners, L.P., an oil and gas transport company that has a 35 percent stake in the Dakota Access Pipeline. Energy Transfer Partners, L.P. has an 8 percent stake in the PES facility, specifically.

Citing health risks to their community, the Standing Rock Sioux Tribe famously resisted the construction of the Dakota Access Pipeline and were met with a notorious display of police violence and brutality. According to the Guardian, more than two dozen demonstrators were hospitalized and more than 300 people were injured during an encounter with police in November 2016. The pipeline was constructed and experienced its first spill in April 2017.

In January, Sunoco paid over $436,000 in civil penalties and response costs after its assets caused three crude oil spills in Texas, Louisiana, and Oklahoma between 2013 and 2015. Sunoco also paid a fine of more than $3.6 million after spilling almost 200,000 barrels of oil at Pennsylvania’s John Heinz National Wildlife Refuge in 2000.

The PES facility was first constructed in 1866, according to the facility website, making it over 150 years old. Facilities such as the PES facility, which are owned and operated by private entities, have little incentive to invest in newer, safer facilities, or facilities that generate clean energy rather than processing fuel. These investments undermine corporate bottom-lines, even when the status quo isn’t profitable.

PES filed for bankruptcy in early 2018. The Environmental Protection Agency gave the company a waiver for half of its $350 million in liabilities for "biofuel credits”—a financial tool similar to carbon credits, which rewards companies for putting some biofuels into their oil products. Biofuel and carbon “credits” are tools that designed to incentivize renewable energy investments, but in practice, they usually encourage complacency.

After exiting bankruptcy in August 2018, PES saw a $61 million decline in its cash balance in just three months, according to Reuters. Ted Cruz blamed the company’s financial difficulties on biofuel credits hindering maximum production.