From Usaf The Army Air Forces In Ww 2 Volume 2 (note the lack of mentioning mustard gas, date 1949)
As if to lend weight to this inference, the GAF carried out on the night of 2/3 December its most successful raid of the year, at Bari. Around thirty aircraft made the attack, coming in behind planes which dropped Window. Normally, a thirty-plane night attack by the Luftwaffe would have produced only limited damage, but this time the enemy enjoyed a freak success. His bombs hit two ammunition ships which blew up in the ship-crammed harbor; the resulting explosions and fires destroyed seventeen ships totaling 62,000 tons and carrying 38,000 tons of cargo (mostly hospital supplies and 10,000 tons of steel plank), caused many casualties, and so damaged the port facilities that Bari's capacity was not back to normal for three weeks. The success of the raid owed much to the enemy's good luck in hitting the ammunition ships and to his skillful use of Window; but the extraordinarily heavy damage occurred because the Allies had unwisely crowded their ships in the harbor. The weakness of fighter and AA defense reflected poor and perhaps inadequate-communications, incomplete liaison among the several defensive elements, and insufficient guns and searchlight
The Bari raid caused renewed concern for the safety of Allied bases and installations in eastern Italy.a7 It indicated that the Germans were in a position to launch sudden and even heavy attacks anywhere in the central Mediterranean because of the large number of air bases which were available to them in Italy and the Balkans. This conclusion appeared to be confirmed on the night of 13/14 December when the GAF again visited Bari. Although the attacking planes did little damage, the raid was significant because the planes came from Greece-the first time that bombers from that area had attacked an Italian target. The Allies drew some comfort from the deduction that the attack had come from Greece probably because the enemy was withdrawing most of his long range bombers from Italy to Germany. Subsequently, this was confirmed by photographic evidence. Captured GAF records revealed after VE-day that at the end of December the enemy's bomber force in the Mediterranean was down to 29 serviceable planes as against 214 on 30 November-which explains why the Luftwaffe, except for its two raids on Bari, seldom bothered the Allies in December