Shares of International Paper, which makes the containerboard used in cardboard boxes and other packaging, rose more than 5% Tuesday on two pieces of good news for the second largest containerboard producer in the U.S.

The first is a containerboard price increase of $80 a ton effective Sept. 1 that Truist analyst Michael Roxland wrote about in a Tuesday morning note. International Paper didn't respond to Barron's request for comment, but the report follows a similar increase of $140 a ton by rival Packaging Corp -- also flagged by Truist -- on Friday that sent paper stocks soaring.

"We believe IP's increase is being driven by higher costs including freight, recycled fiber, chemicals, and purchased electricity, strong demand, and tight supply," Roxland wrote in a Tuesday morning note.

The second bit of good news for International Paper came late Monday from J.P. Morgan, which upgraded the company's stock to Overweight from Neutral and raised its price target to $61 from $51 on expected price increases.

Containerboard consists of two parts: the flat linerboard and the fluted corrugated middle section known as corrugated medium. A cardboard box is typically made of one piece of corrugated medium sandwiched between two pieces of linerboard. Current prices are $1,045 a ton for linerboard and $935 a ton for corrugated medium, Roxland noted. An $80 price increase works out to a 7.7% and 8.6% bump, respectively, for each part.

International Paper stock has been on a roll since Friday, when it rose 11.2% to make it the top performer in the S&P 500 that day. It has risen 17% over the past three trading days, but is down 18% over the past 12 months.

Other paper stocks were rising Tuesday as well, including Packaging Corp and Smurfit Westrock, which were up 1.4% and 3.2%, respectively.