If there’s ever a remake of the blockbuster musical “Carousel,” its most catchy tune, “June Is Busting Out All Over,” might appropriately be sung by a chorus of those regulators who police Wall Street.

Why so? Because this month has seen an unusual outburst of stock trading investigations commenced by the Securities and Exchange Commission. In all, the SEC has kicked off at least 13 such probes within the past two weeks, with five of them centered in the energy sector, I’m told.

The commission, as usual, declined to comment on the investigations, of which none have been reported, but a regulatory contact with close ties to the SEC confirmed the probes, 10 of which involve companies whose shares are traded on the New York Stock Exchange.

Those people who refuse to operate in the securities market on a level playing field – the ones who relish the cheating game – will never learn, says one regulator, who estimates that this year’s stock trading investigations at various exchanges and regulatory agencies are up an average of between 10% and 15% from last year. While the usual leaks stemming from the stepped-up outbreak of merger-mania might well be viewed as the chief catalyst for such a rise, in fact the majority of investigations transcend that arena and have nothing to do with the M &A rage, the regulator tells me.

As part of its investigations, the SEC has recently fired off letters to the brokerage community in which it requested the names of any of the firms’ clients or employees who traded in either the shares or options of the 13 companies during specified time periods. The investigations, which are being handled out of the agency’s Washington office, focus on the following companies:

* Plains All American Pipeline ($46.14), which owns and operates about 15,000 miles of pipelines throughout Canada and America. The company is 17% owned by Vulcan Energy, which is controlled by a Microsoft co-founder, Paul Allen.

* Southwestern Energy ($27.02), an oil and gas exploration and production company in the Southwest.

* Genesis Energy ($12.36), which buys and aggregates crude oil at the wellhead and makes bulk purchases at terminal and pipeline facilities for resale.

* Regal Beloit Corporation ($44.07), a manufacturer of motion control and power transmission products.

* Geron Corporation ($6.74), which collates and processes tires.

* Las Vegas Sands ($65.88), a hotelcasino resort operator.

* Hornbeck Offshore Services ($32.96),which provides marine transportation of oilfield equipment, supplies, and petroleum products.

* Technical Olympic USA ($14.50), a homebuilder that operates nearly 250 communities in Florida, Texas, and western and mid-Atlantic states.

* Taiwan Semiconductor ($8.78), operator of the world’s largest semiconductor foundry.

* L.G. Philips LCD ($17.21), one of the world’s top producers of thin-film transistor liquid crystal displays.

* Nalco Holding ($16.92), the world’s largest maker of chemicals used in water treatments.

* Capital Title Group ($7.62), a provider of title insurance and escrow services, primarily in the Southwest.

* Enterprise Products Partners ($24.67), a leading player in North American natural gas, natural gas liquids, and the crude oil industries.

What do these investigations all mean to the average investor who may own the companies’ shares? Not, it should be stressed, that there’s necessarily anything materially wrong at the companies, but rather that the commission suspects a violation may have occurred in the trading of the shares, possibly the illegal use of inside information.

About the only thing an SEC spokesman, John Nester, would say about the agency’s investigations in general is that there are about 2,000 underway.

dandordan@aol.com