Six Flags said it plans to add seat belts to some of its roller coasters following a deadly incident this month at its Georgia theme park. In a letter to guests and passholders late Friday, Six Flags Chief Executive John Reilly said the additional restraints would be added to the Goliath coaster at Six Flags Over Georgia and similar rides at its other parks. Those rides already feature "clamshell" lap bars to keep guests in their seats. Hassan Jihad Ibn Kariem, 42, died earlier this month after he fell from the Goliath. Investigators believe he was ejected from his seat. Four other passengers were injured. The Georgia coaster, which was touted as a "steel monster" when it first opened two decades ago, reaches a height of 200 feet and speeds up to 70 miles an hour. Six Flags is also hiring independent engineers and ride-inspection professionals to review safety procedures across all its rides, Reilly said. "We are committed to carefully evaluating their findings and taking appropriate action to further strengthen our standards and culture of safety," he said. Goliath and eight other rides at five of the company's parks remain closed as the investigation into the accident continues, the letter said. Before the accident, Six Flags had faced scrutiny over the safety record associated with another of its attractions: the X2 coaster at its Magic Mountain park in Southern California. Multiple lawsuits alleged that the coaster caused serious brain injuries. Six Flags permanently closed that ride last month. The company had said before this month's death that ride reliability to ensure they don't break down was a focus of its efforts to improve operations and boost profit. During a recent earnings call with analysts, Reilly said the company had invested more in repairs and maintenance at certain parks in a bid to increase guest satisfaction.