Nikola, a startup company that makes electric and hydrogen-powered semi trucks, said in a tweet Friday morning that several of its trucks had been damaged in a fire at the company’s Phoenix, Arizona headquarters. “Foul play is suspected as a vehicle was seen in the area of the affected trucks just prior to the incident and an investigation is underway,” the tweet said. A Nikola spokesperson reached by CNN said more information would be released as it became available. The first report of a fire was around 4:30 am MT, Phoenix Fire Department captain Todd Keller said. By around 8:00 am Phoenix time, fire crews were still spraying water on the five trucks to try to cool the battery packs enough to move them into large storage bins where they could be covered in sand or water, Keller said. Fires involving electric vehicle batteries can be difficult to get under control. Given the large amount of energy stored in the batteries, fires that have been extinguished can reignite later through chemical reactions. The trucks were among more than 30 stored at the headquarters facility, Keller said. He could not say whether arson could be a factor until the fire department completed its investigation, a process that could take days or even weeks, Keller said. Nikola’s stock price dropped roughly 8% by late afternoon on Friday. Executives with the company are currently seeking shareholder approval for a reverse stock split intended to boost the company’s stock price, which currently stands at about $1.30 a share. The company has also announced that is sharply cutting spending. In 2020, Nikola was the subject of a scathing report by Hindenburg Research, an investment fund that researches companies, shorts their stock, and subsequently publishes reports alleging shortcomings. The report alleged, among other things, that the company overstated how far along prototypes were and the value of some business deals. Nikola said at the time that the charges were false.