The Merrimack Valley gas disaster has cost Columbia Gas more than $1 billion, according to a financial report filed by its parent company.

In a 2018 financial report filed this week, NiSource, parent company of Columbia Gas, reported a loss of $757 million for third-party claims including property damage, and $266 million in losses for other incident-related expenses.

The company wrote in the filing that it expects the financial losses to increase.

On Sept. 13, an over-pressurized natural gas line caused explosions and fires in homes and other buildings across Lawrence, Andover and North Andover, displacing thousands of residents and killing 18-year-old Leonel Rondon.

Lawrence Mayor Daniel Rivera, who had called for the dissolution of the company in the wake of the disaster, called the losses simply the "cost of doing business."

"The loss of $1 billion from Columbia Gas is nothing compared to the loss of life and property that the three communities in Greater Lawrence have lost," he said. "Someone retired with full benefits, and no one has been fired or disciplined for what happened that day. If all they lose is money, why would they change anything? They can just chalk it up as the cost of doing business."

Earlier this month, President of Columbia Gas of Massachusetts Steve Bryant announced he would retire in May — after pledging his commitment to the recovery in a congressional hearing in Lawrence where he said he had no plans to resign.

The amount of financial losses to the company does not include the estimated cost of pipeline replacement. The company spent $167 million replacing pipelines in the area in 2018, and estimates it will cost between $220 million and $230 million to complete the task, according to company officials.

The losses recorded in the filing also do not include the costs of settlements from lawsuits of the Rondon family or class-action settlements.

The disaster remains under investigation by the National Transportation Safety Board.

Expenses from the incident have exceeded the insurance coverage for the company, according to the report.

"Total expenses related to the incident have exceeded the total amount of liability insurance coverage available under our policies," the company wrote in the financial report, noting the company may be unable to obtain insurance on acceptable terms.

"We expect the premiums we pay for our insurance coverage to significantly increase as a result of the Greater Lawrence Incident and market conditions," according to the report.