BERLIN (AP) — Germany's Bayer says the number of plaintiffs who have filed lawsuits against subsidiary Monsanto over its Roundup weed killer in the United States swelled by 5,000 in the second quarter to about 18,400.

Bayer, which detailed the total number of plaintiffs as of July 11 in its quarterly report released Tuesday, said that "we continue to believe that we have meritorious defenses" and will "defend ourselves vigorously."

The company said that it also faces five Canadian lawsuits seeking class-action certification.

Plaintiffs claim that Roundup caused cancer and rulings in three cases in the U.S. have gone against Monsanto. Bayer argues that studies have established that glyphosate, Roundup's active ingredient, is safe.

Bayer acquired Monsanto for $63 billion last year.