Constellation Energy Group of Baltimore, the parent of Baltimore Gas & Electric, said third-quarter profit fell 12 percent, pulled down by sales of power at fixed prices while costs for fuel and purchased supplies of electricity surged.

Earnings fell to $185.5 million ($1.03 a share), from $210.4 million ($1.19) a year earlier. Sales rose 47 percent, to $4.92 billion from $3.36 billion.

Hotter weather in the third quarter increased demand for electricity from customers such as Staples and Supervalu paying fixed rates, prompting Constellation to buy more costly power from other suppliers. Combined costs for such purchased power and for power-plant fuel surged 71 percent from a year earlier to $3.95 billion, the company said. Shares closed at $54.20, down 20 cents.

* GTSI, a Chantilly government technology contractor, earned $4.2 million (44 cents a share) in the third quarter, down 60 percent from a profit of $10.5 million ($1.13) in the same period a year ago. Revenue was $287.6 million, down 13 percent from $330.6 million. The company said it has surmounted "immense difficulties" with a new internal computer system, and shares closed at $7.90, up 59 cents, or 8 percent.

* Gene Logic, a Gaithersburg company that supplies genetic services to drug companies, lost $39.5 million ($1.24 a share) in the third quarter, compared with a loss of $14.6 million (46 cents) a year earlier. Revenue was flat at $17 million. Shares closed at $3.90, down 39 cents, or 9 percent.

* VSE, a government contractor based in Alexandria, earned $1.6 million (66 cents a share) in the third quarter, up from $885,000 (38 cents) a year earlier. Revenue was $76.6 million, up 23 percent from $62.2 million a year earlier.

* First Potomac Realty Trust, a real estate investment trust based in Bethesda, reported funds from operations of $8.3 million (46 cents a share) for the third quarter, compared with $4.6 million (29 cents) a year earlier. Profit was $1.6 million (9 cents), up from $657,151 (5 cents). Revenue was $20.7 million, up 70 percent from $12.2 million.