It was a late night in late August when an employee at a Lime scooter facility in Tahoe, heard a loud bang. One of the bright-green rental scooters – which have meteorically swarmed streets in crowded cities around the world over the past year – had burst into flames, seemingly, all on its own.

According to a blog posted by Lime on Tuesday, nearly two months later, bad batteries were to blame. Stating that the defect had affected less than 0.01% of the “fleet”, the company conceded that a “manufacturing defect could result in the battery smoldering, or in some cases, catching fire”.

It’s the latest controversy over the dockless scooters, that have spread to cities across the globe in recent years. The Washington Post, which first reported the story, found that employees had alerted the company to potential issues and felt they had not been adequately addressed, putting riders and “juicers”, people paid to charge the scooters overnight, at unnecessary risk.

Since starting just over a year ago, Lime boasts it has millions of riders. The company emphasized in its response that it has taken extra precautions to ensure the safety of anyone who uses or charges its scooters.

Writing that the batteries were manufactured by Segway Ninebot, a company merged from a Chinese company and an American one that produces transportation products, Lime stated it had created software to detect any that were defective. Then, it made a second software program to find all the Scooters that might have one, bringing them all home to local headquarters.

“When an affected battery was identified – with a red code – we promptly deactivated the scooter so that no members of the public could ride or charge it,” the company wrote in the statement.

Reiterating that it did not want to take any chances, it also will now have employees familiar with the issue on hand for 24 hours a day at facilities where the Segway Ninebot Scooters are held and will run daily diagnostics on all scooters, regardless of where they were made and if they might have rogue batteries.

But according to Lime mechanics, who spoke anonymously to the Post, their concerns over the scooters were dismissed by senior staff, especially over the safety of “juicers” who may have unknowingly charged machines with potentially dangerous defects.

“These people are plugging these scooters into their house at night and going to sleep thinking they’re safe and that they just earned an easy $15,” one employee told the Post. “When I asked my managers if we were going to tell them all I got was shrugged shoulders and ‘I don’t know’.”

Others voiced frustrations in their mechanic Slack chat, calling for the company to remove the scooters from the market until the issues were better addressed.

“I get that the scoots are expendable and replaceable,” one person wrote. “But are we now resigned to say the same for the safety of employees and customers?”

This isn’t the first safety issue raised, as scooter companies have rapidly descended on cities around the world. Seen as either the scourge or saviors in crowded cities, where cheap, efficient transportation is scarce, proponents have argued for their use as a sustainable solution, while critics point out the dangers.

Scooter-caused emergency-room visits are becoming increasingly common, and there have been allegations that the proper upkeep has not been done by startup scooter companies.

In cities like San Francisco, the response was swift, and scooters that did not end up in trashcans or in local lakes were taken off the streets by regulatory officials, before they were brought back in smaller doses. Other cities are working to create better scooter rules, as scooter startups continue to increase their scale.

Lime disputes any questions over its intentions, and emphasized safety is of utmost importance. “Lime takes full responsibility for our scooters,” it wrote. “The safety of our riders, Juicers, and community is our highest priority, and we will continue to hold our equipment manufacturers and ourselves to the highest possible standard.”