DENVER -- Major League Baseball has sent an official to investigate a temperature-controlled environmental chamber used by the Colorado Rockies for storing baseballs, according to a published report.

Though baseball is satisfied with the chamber's purpose of preventing the balls from drying out, the commissioner's office indicated that it was disappointed the Rockies built and used the chamber without taking necessary steps for approval, The Denver Post reported Sunday.

The Rockies didn't disclose that they were using the device until Tuesday.

"The secretive nature was unfortunate," said Sandy Alderson, vice president for the commissioner's office and a member of baseball's rules committee. "It contributed to the perception that the Rockies have done something wrong. Had they informed us of their intentions, we would have given our approval because what they are doing is in compliance of what the ball manufacturer would recommend."

The chamber, which works much like a cigar humidor, is designed to keep balls from drying out and shrinking in the low humidity of Denver. The idea is to make the balls easier to grip for pitchers and harder for batters to hit out of the ballpark.

To maintain the baseballs at specifications, the Rockies set the chamber at 40 percent humidity. The chamber is designed to hold 500 dozen baseballs, which are dated and rotated.

The Rockies have been using the chamber for about three weeks.

The humidor has set off a national debate, with critics citing statistical evidence that the humidity-stored baseballs have greatly affected games at Coors Field and proponents saying it's a great way to combat the effects of altitude. The Rockies have said they are merely preserving, not altering, the baseball.

The Rockies initially said the chamber was approved by the commissioner's office, but Alderson challenged that on Friday.

Keli McGregor, the Rockies president, indicated that he didn't feel a need to draw attention to a storage system that was merely meant to help conform to the rules.

"We're doing something that is right," McGregor said. "All that matters here is we are trying to maintain the baseballs to spec. I challenge you to look at where they store the baseballs in 29 other places and find one that does a better job of maintaining the baseballs to spec. Everything we're doing is right, and the notion that we are altering the baseball is offensive to me."