What happened

Shares of General Motors (GM -1.73%) were trading lower on Thursday, as investors braced for grim April auto sales results and digested a report that GM could be dragged into an ongoing federal investigation of the United Auto Workers (UAW) labor union.

As of noon EDT today, GM's shares were down about 5.1% from Wednesday's closing price.

So what

There are a few things that could be weighing on auto investors' minds on Thursday. 

First, analysts expect April to be the worst month for U.S. auto sales in 30 years. Analysts at Edmunds are forecasting that just 633,260 new cars and trucks will have been sold in the U.S. in April, which would be a decline of 52.5% from April 2019. Edmunds said that would be the lowest-volume month for U.S. auto sales since at least 1990.

GM's corporate headquarters in downtown Detroit.

Image source: General Motors.

Second, The Wall Street Journal reported that an ongoing federal investigation of corruption at the UAW has expanded to involve GM. FBI agents have interviewed current and former GM employees and requested thousands of documents, raising questions about interactions between GM's bargaining team and its counterparts at the UAW, the Journal reported. 

It's not clear whether the investigation is targeting any current or former GM employees. The company said in a statement that it has been cooperating with the government for nearly three years. But it's not surprising that investors might be concerned, as the probe has already led to 13 convictions, including former employees of Fiat Chrysler Automobiles. 

Third, rival Ford Motor Company (F -3.30%) reported earnings on Tuesday after the market closed. They were as expected (a net loss of $2 billion), but it was the company's guidance that raised eyebrows, and may be weighing on GM's stock today. Ford expects an adjusted operating loss of at least $5 billion in the current quarter. 

Now what

Investors won't have to wait long for an update from CEO Mary Barra and her team. GM will report its own first-quarter results before the market opens next Wednesday, May 6.