Private-equity firm New Mountain Capital LLC is in advanced talks to buy laboratory equipment supplier VWR Corp. in a deal that could be valued at nearly $5 billion, the Wall Street Journal reported, citing sources.

The talks may yield a deal as soon as this week, people familiar with the matter told the newspaper, assuming they don't fall apart.

Shares of VWR were up 26.2 percent at $36.00 in afternoon trading on Wednesday.

VWR, which sells laboratory products such as chemicals, reagents, consumables and scientific instruments, had market capitalization of $3.76 billion as of Tuesday's close, according to Reuters data.

Both companies were immediately unavailable for comment.